OBS MKV to MP4: Remux Recordings Without Re-encoding

If your video editor will not open an OBS recording saved as MKV, try File → Remux Recordings in OBS before running the footage through a video converter. Remuxing puts the existing audio and video into a different container. It avoids another round of video compression, although the receiving app still needs to support the codecs inside the file.

The workflow below covers an existing OBS MKV recording on Windows and the choice of format for your next recording. The interface steps follow OBS’s published guides; this is not a hands-on comparison of video editors.

A new container keeps the same recorded picture

MKV and MP4 are containers: they organise video, audio and related information in a file. A codec, such as H.264 or AV1, describes how the picture is encoded. OBS’s audio and video formats guide lists those choices separately because a supported container does not guarantee support for every codec combination.

Remuxing changes the packaging while copying the encoded streams. Transcoding decodes media and encodes it again, which is the route for changing a codec or applying changes to the picture. FFmpeg’s streamcopy documentation explains why copying streams avoids encoding quality loss, and why some source material cannot be put into a particular destination container.

That distinction sets expectations. A remux will not sharpen a blurry capture, remove stutter already recorded, or create a much smaller video through stronger compression. It also does not mean the MKV and MP4 files will be identical byte for byte: their packaging differs.

Remux one recording in OBS

Keep the original MKV and choose a destination with room for a second copy.

1. Finish the recording and wait for OBS to stop writing it.
2. In the main OBS window, open File → Remux Recordings.
3. Use the … control to select the MKV recording.
4. Check the target file’s name and location. Keep it distinct from any MP4 you want to preserve.
5. Select Remux and wait for the completion message.

These controls are documented in OBS’s Standard Recording Output Guide . You do not need to choose a new bitrate or quality preset for this operation.

Before deleting anything, open the resulting MP4 in the application you actually intend to use. Scrub near the start, middle and end, listen to the audio, and import the file into a small editing project. A successful remux message confirms that OBS completed its operation; the editor check answers whether the result fits your workflow.

Missing microphone audio may be a track-selection problem

OBS can record different audio sources to separate tracks. Its multitrack recording guide explains that ordinary players generally play one track at a time, while an editor with multitrack support can expose them separately.

For example, suppose you recorded game audio on one track and your microphone on another. Hearing only the game in a player is not enough to conclude that the microphone disappeared. Inspect the available audio tracks in the editor and listen to each intended track before discarding the original.

Remuxing also cannot recover sound that was never recorded. For your next session, make a short test containing both game sound and a spoken phrase. Confirm those sources in the recording itself, rather than relying only on moving meters in OBS.

If the MP4 still will not import, check its codecs

The extension is only part of the compatibility check. OBS documents broad H.264 and AAC support, while other video and audio formats have different editing support. An AV1 recording remains AV1 after remuxing; putting it in MP4 does not turn it into H.264. The same distinction applies to audio. OBS’s format compatibility tables are a useful starting point.

Check your editor’s documentation for the exact video codec, audio codec and software version. If those codecs are unsupported, another remux may not solve the problem. You may need a transcode to a supported combination, with the quality, processing time and storage consequences that entails. Keep the original as the source for that conversion.

Choose deliberately between MKV and Hybrid MP4 next time

Traditional MP4 recording relies on final metadata that is normally written when recording stops. If writing is interrupted before that information is saved, recovery can be difficult or impossible. The OBS developer’s July 2024 explanation of its MP4 muxer describes this failure mode.

Hybrid MP4 takes a different approach. During recording, it uses fragments that reduce dependence on one final index. On a normal stop, OBS performs a “soft remux” so the result behaves like a regular MP4. OBS introduced this format in 30.2; its 32.0 release notes , dated 22 September 2025, say Hybrid MP4/MOV left beta and became the default for new profiles.

For a Windows workflow that needs MP4, Hybrid MP4 is therefore worth trying with your editor before a long recording. You do not have to switch a working profile to MKV solely because an older guide warns about traditional MP4.

MKV followed by remuxing remains a useful deliberate choice. If you always want an MP4 copy, OBS also offers Settings → Advanced → Automatically remux to mp4, which runs after recording stops. The standard output guide documents that setting. Allow space for both files and check the finished copy before removing the source.

Neither format replaces a backup of a recording you cannot repeat. Use a short trial in your actual editor to settle the choice, then keep the original footage until the edited result is safely saved.